| Year | Value | | 2021 | 35.128677158918 | | 2020 | 35.096930994625 | | 2019 | 35.064076645865 | | 2018 | 35.03234596115 | | 2017 | 35.000615276435 | | 2016 | 34.816911312297 | | 2015 | 34.633207348159 | | 2014 | 34.688133954469 | | 2013 | 34.74306056078 | | 2012 | 34.797987167091 | | 2011 | 34.852913773402 | | 2010 | 34.907840379713 | | 2009 | 35.305871495122 | | 2008 | 35.70390261053 | | 2007 | 36.101933725938 | | 2006 | 36.499964841347 | | 2005 | 36.897995956755 | | 2004 | 37.296027072163 | | 2003 | 37.694058187571 | | 2002 | 38.09208930298 | | 2001 | 38.490120418388 | | 2000 | 38.888151533796 | | 1999 | 39.360881603235 | | 1998 | 39.833611672673 | | 1997 | 40.306341742111 | | 1996 | 40.77907181155 | | 1995 | 41.251801880988 | | 1994 | 41.724531950426 | | 1993 | 42.197262019865 | | 1992 | 42.669992089303 | | 1991 | 43.142722158741 | | 1990 | 43.61545222818 |
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